Projectile detection system

1. A bullet detection system for use on a vehicle, the bullet detection system comprising: a radar antenna array arranged to transmit and receive microwave signals so as to provide a plurality of detection segments of a volume of airspace and comprising a plurality of transmitters, each transmitter in the plurality being arranged relative to a first beam shaping means to transmit microwave signals into a respective segment of the plurality of segments; a plurality of receivers, each receiver being arranged relative to a second beam shaping means to receive microwave signals reflected by the bullet from a respective segment of the plurality of segments; and shielding means arranged to prevent microwave signals transmitted from a transmitter being directly received by the at least one receiver without first being reflected by an object; one or more processors configured to: determine which segments of the plurality of segments received microwave signals reflected by the bullet are received from; determine timing information relating to a time order in which the received microwave signals are received in each segment microwave signals reflected by the bullet are received from; and determine directional information relating to a direction of travel of the bullet from segment to segment based on the determined segments in which the received microwave signals reflected by the bullet are received from and the determined timing order in which the received microwave signals are received; wherein the microwave signals have a frequency between 1 GHz and 30 GHz.

2. A projectile detection system according to claim 1 , wherein the microwave signals have a frequency between 7 GHz and 17 GHz.

3. A projectile detection system according to claim 1 , wherein the microwave signals have a frequency between 10 GHz and 14 GHz.

4. A projectile detection system according to claim 1 , wherein the microwave signals have a continuous waveform.

5. A projectile detection system according to claim 1 , wherein the volume of airspace is a volume of airspace substantially surrounding a portion of the vehicle.

6. A projectile detection system according to claim 1 , wherein at least two of the segments overlap to some extent.

7. A projectile detection system according to claim 1 , further comprising means for determining a radial velocity of the projectile.

8. A projectile detection system according to claim 7 , wherein the means for determining a radial velocity of the projectile is adapted to determine a radial velocity of the projectile using a Doppler profile of the received microwave signals.

9. A vehicle comprising a projectile bullet detection system, the bullet detection system comprising: a radar antenna array arranged to transmit and receive microwave signals so as to provide a plurality of detection segments of a volume of airspace and comprising a plurality of transmitters, each transmitter in the plurality being arranged relative to a first beam shaping means to transmit microwave signals into a respective segment of the plurality of segments; a plurality of receivers, each receiver being arranged relative to a second beam shaping means to receive microwave signals reflected by the bullet from a respective segment the plurality of segments; and shielding means arranged to prevent microwave signals transmitted from a transmitter being directly received by the at least one receiver without first being reflected by an object; one or more processors configured to: determine which segments of the plurality of segments received microwave signals reflected by the bullet are received from; determine timing information relating to a time order in which the received microwave signals are received in each segment microwave signals reflected by the bullet are received from; and determine directional information relating to a direction of travel of the bullet from segment to segment based on the determined segments in which the received microwave signals reflected by the bullet are received from and the determined timing order in which the received microwave signals are received; wherein the microwave signals have a frequency between 1 GHz and 30 GHz.

10. A vehicle comprising according to claim 9 , wherein the vehicle is an aircraft.

11. A method of detecting a bullet comprising: transmitting microwave signals from a plurality of transmitters, each transmitter in the plurality being arranged relative to a first beam shaping means to transmit microwave signals into a respective segment of a plurality of detection segments of a volume of airspace; receiving microwave signals from a plurality of receivers, each receiver being arranged relative to a second beam shaping means to receive microwave signals reflected by the bullet from a respective segment of the plurality of segments; and processing the received microwave signals by a processor comprising hardware and instructions causing the processor to perform the steps of: determining which segments of the plurality of segments received microwave signals reflected by the bullet are received from; determining timing information relating to a time order in which the received microwave signals are received in each segment microwave signals reflected by the bullet are received from; and determining directional information relating to a direction of travel of the bullet from segment to segment based on the determined segments in which the received microwave signals reflected by the bullet are received from and the determined timing order in which the received microwave signals are receive; wherein the microwave signals each have a frequency between 1 GHz and 30 GHz.

12. A method according to claim 11 , wherein the microwave signals each have a frequency between 7 GHz and 17 GHz.

13. A method according to claim 11 , wherein the microwave signals each have a frequency between 10 GHz and 14 GHz.